The present invention relates generally to pneumatic rail brake systems and more specifically to improved components for the system.
The prior art brake systems were generally standardized to include an ABD or equivalent braking valve connected by conduits to the brake pipe, auxiliary and emergency reservoirs and brake cylinders. These brake valves would control all the brakes on the trucks of a single car. If more than two trucks were to be controlled by the brake valve, relay valves were included. These systems include a substantial amount of conduits connecting the elements of the brake system on each of the cars. The ABD and equivalant brake valves include the service application, emergency application, release and accelerated release function. With the development of non-conventional car designs, brake systems which are adapations of the preexisting brake systems were developed. These and the conventional brake systems include an unnecessary amount of conduits per car and unnecessarily large reservoirs.
Thus, it is an object of the present invention to provide a simplified fluid brake system for rail vehicles.
Another object of the present invention is to provide a braking system which reduces the size of the auxiliary and emergency reservoirs.
A further object of the present invention is to eliminate unnecessary piping and reduce the number of sources of fluid leakage.
Another object of the present invention is to provide a group of standard parts or modules which can be economically applied to any type of freight car without special engineering, including articulated cars having any number of trucks between couplers.
These and other objects of the invention are attained by providing a triple valve assembly having reduced auxiliary and emergency reservoirs mounted directly thereon. The assembly is connected only to the brake pipe and to the brake cylinder of one truck and controls the interconnection between the brake pipe, brake cylinder, auxiliary reservoir and emergency reservoir to produce charging of the reservoirs, service application and emergency application of the brakes and release of air to the brake cylinder. The unique triple valve, in response to the venting of brake pipe which characterizes an emergency brake application, provides a sequential application of pressure to the brake cylinder. First the auxiliary reservoir pressure is equalized with that of the brake cylinder, followed by disconnection of the auxiliary reservoir from an application of the emergency reservoir to the brake cylinder. This sequential operation allows increased brake cylinder pressure while allowing reduction in the volume of the emergency reservoir used to accomplish this pressure.
In both service and emergency applications, a variable flow rate valve is connected between the supply portion of the triple valve and the brake cylinder to allow a high flow during the initial application of the air to the brake cylinder with a decreased flow rate during the second stage.
The triple valve assembly is easily adaptable for receiving a load responsive fixture. This fixture includes a first path for connecting the supply to the brake cylinder and to a volume reservoir and providing a predetermined portion of supply pressure to the brake cylinder. A second path controlled by the load is connected in parallel with the first path, and bypasses the proportioning path and cuts off the volume reservoir for a loaded sensed condition. A double acting piston is provided to simultaneously open the bypass and close the dummy reservoir or connect the dummy reservoir and close the bypass. The bypass is also responsive to a brake released signal to bypass the proportioning device during a brake release sequence.
A modulating valve is also provided independent of the triple valve assemblies, which enhances brake pipe pressure reduction by filling a quick service volume with fluid from the brake pipe for a service signal, and sequentially venting a bulb volume to the atmosphere and refills the bulb volume from the brake pipe as a function of the magnitude of the service signal. The modulating valve also charges the brake pipe with previously stored fluid so as to enhance the rise of brake pipe pressure, hence release of the brakes from a release reservoir in response to a release signal. The filling of the quick service volume occurs at a rate controlled as a function of the differential pressure between the release reservoir and the brake pipe. A quick action chamber is included for providing accelerated response for filling the quick service volume and venting the bulb volume. The quick action chamber is vented after the accelerated initiation and has no effect during further brake pipe pressure reduction activity.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.